What kind of concept is the Augenblick? We know how to deal with it because it occupies a definite position within the lucid architectonic of Being and Time, as the name for authentic temporality and historicity. But when we approach it, it nevertheless tends to slip away--not for dialectical reasons, as the Aristotelian now, but precisely because it pretends to escape this inherited logic of temporality altogether. It claims to name a present that is not the present of the now-point, not the extended Husserlian present of retention and protention, but a constitutive present out of which the temporal scheme can emerge as such. Such a present is not and can never be present. As a locus of decision and authentic resolve, it nevertheless withdraws from conceptual reach.
This logic of withdrawal and restraint is not made explicit by Heidegger in connection with the Augenblick, even though it is implied by the way it operates in his thinking. It is only in the thought of Ereignis that this curious mode of being and of signifying is made into a theme in itself. Ereignis is also Enteignis, it is withdrawal and disappropriation. It is a basic concept that disavows the idea of conceptual hierarchy; it is a name for the origin, yet does not designate anything. What kind of a word is it? What kind of understanding, indeed, what kind of thinking and reasoning does it encourage us to perform? It seems to hold out a promise for those who are prepared to seek out the limit of discursive thought, as it pretends to name the very element of thinking, of understanding, and of truth.
P. 246-247